Propellant charge for telescoped caseless ammunition having a deterrent-coated aft-end

ABSTRACT

An improved propellant charge for telescoped caseless ammunition is provided. A telescoped caseless round is a caseless round in which the projectile is fully contained within an axial bore in the propellant charge. The propellant charge has a burning rate deterrent applied to its aft-end which results in improved ballistic performance for the round.

United States Patent Inventor Joseph I. Harrell Sussex, N.J.

Appl. No. 861,885

Filed Sept. 29, 1969 Patented Dec. 2], I971 Assignee HerculesIncorporated Wilmington, Del.

PROPELLANT CHARGE FOR TELESCOPED CASELESS AMMUNITION HAVING ADETERRENT-COATED AFT-END 11 Claims, 3 Drawing Figs.

US. Cl 102/38, l02/DIG. 1 Int. Cl F42b 5/18, F42b 9/16 [50] Field ofSearch 102/38, DIG. l, 104

[56] References Cited UNlTED STATES PATENTS 1,454,4l4 5/1923 Skilling102/104 X 1,661,278 3/1928 Troxler [02/104 UX 3,482,5l6 12/1969 Farmeret al. 102/38 Primary Examiner- Robert F. Stahl Attorney-Michael B.Keehan ABSTRACT: An improved propellant charge for telescoped caselessammunition is provided. A telescoped caseless round is a caseless roundin which the projectile is fully contained within an axial bore in thepropellant charge. The propellant charge has a burning rate deterrentapplied to its aft-end which results in improved ballistic performancefor the round.

DEBZ] 197i FIG. I

FIG.3

JOSEPH I. HARRELL INVENTOR BY i/MZz 5 ATTORNEY PROPELLANT CHARGE FORTELESCOPED CASELESS AMMUNITION HAVING A DETERRENT-COATED AFF- END Thisinvention relates to telescoped caseless ammunition having improvedballistic performance. More particularly, this invention relates to amolded propellant charge for telescoped caseless ammunition in which atleast a portion of the surface area provided by the propellant granulescomprising the aftend of the the propellant charge is coated with aburning rate deterrent.

Telescoped caseless ammunition is comprised of a propellant charge, aprojectile, and a primer. The propellant charge has an axial cavityequal to or greater than the length of the projectile. The projectile ishoused completely within the axial bore of the propellant charge. Aprimer is positioned behind the projectile. Various embodiments oftelescoped caseless ammunition are disclosed in U.S. Pat. No. 3,482,516,filed Dec. 28, [967 by L. J. Farmer et al., and entitled CaselessCartridges Having the Projectile House in the Propellant Charge."

When a telescoped round of caseless ammunition is loaded into thechamber of a gun, the projectile, which is housed in the propellantcharge, is not seated in the barrel of the gun as is the projectile of aconventional round of ammunition when in a loaded position. Uponinitiation of the primer of the telescoped round, the projectile isforced forward through the axial cavity in the propellant charge intothe barrel of the gun and is seated therein. The projectile issubsequently ejected or "fired" from the gun due to rapid pressurebuildup in the chamber and barrel of the gun resulting from burning ofthe propellant charge. The steps in the firing process of a gun asheretofore described are continuous and take place in very rapidsuccession, on the order of a few milliseconds. Prior to seating of theprojectile in the barrel of the firearm, combustion gases from theinitiated primer and propellant charge can escape ahead of theprojectile. If these cases do escape ahead of the projectile, there is aloss of ballistic efficiency for the round.

Propellant charges for caseless ammunition are prepared from moldedgranules of smokeless powder which can be of the single-base,double-base or triple-base types. In order for the molded propellantcharge to function as a typical gun propellant charge, it is necessarythat the individual propellant granules comprising the charge break upand burn as individual granules during a firing. To achieve theforegoing result, propellant charges for caseless ammunition are moldedfrom granules of smokeless powder under controlled conditions employingeither binders for the powder or solvents to soften the surface of thegranules of powder to aid in holding the molded granules in aconsolidated mass. These molded granules retain their individualidentity in the charge. Propellant charges for caseless ammunitionprepared by molding processes have interstitial passages between andaround individual propellant granules throughout the charge.

It is the principal object of this invention to provide a propellantcharge for telescoped caseless ammunition of the type heretoforedescribed which provides improved ballistics for telescoped caselessammunition by reducing gas loss from an initiated propellant charge.

It is another object of this invention to provide a process forpreparing propellant charges for telescoped caseless ammunition havingimproved ignition characteristics.

Other objects of this invention will, in part, be obvious and will, inpart, appear hereinafter. For a complete understanding of the nature andobjects of this invention, reference is made to the following detaileddescription.

The propellant charge of this invention is prepared by a processcomprising contacting the aft-end of the charge with a burning ratedeterrent. The burning rate deterrent must be applied as a liquid or asa solution of a solid burning rate deterrent dissolved in a solventtherefor. The burning rate deterrent can therefore pass throughout theinterstitial passages in the aft-end of the charge whereby the deterrentis deposited over the internal and external surfaces comprising theaft-end of the propellant charge.

The aft-end of the propellant charge as the term is used herein isdefined in relation to the projectile fully contained within the axialbore of the propellant charge. Projectiles for ing surface of theprojectile is the forward surface ofthe rotatl ing band. The initialcontacting surface of a pointed projectile having a guilding metaljacket with the rifling in the barrel of the gun is the base of theogive of the guilding metal jacket.

The contacting surface of a projectile is the basis on which the forwardsurface of the aft-end of the propellant charge of this invention isdefined. If a plane is passed through the contacting surface of theprojectile in an assembled round of telescoped caseless ammunition andthrough the propellant charge, the surface defined by the plane passingthrough the propellant charge is defined as the forward surface of theaftend of the charge. Thus, the aft-end of the propellant charge is thatpart of the propellant charge measured from the aft-surface of thepropellant charge to the surface defined by a plane passing through boththe propellant charge and through the contacting surface of theprojectile. Thus the size of the aftend of the propellant charge willvary with projectile employed in the telescoped round, and in particularwill depend upon the position of the contacting surface of theprojectile in the telescoped round.

In the preferred embodiment of this invention the total surface area ofthe aft-end of the charge is coated with burning rate deterrent. Atleast 10 percent of the total surface area of the aft-end of thepropellant charge measured from the aftsurface of the aft-end of thecharge should be coated with burning rate deterrent in order to achieveany appreciable improvement in ballistics. It is assumed for purposes ofmeasuring the surface area, that the total surface area of the aft-endof the propellant charge, i.e., internal and exterior surface area, islinearly uniform.

The following drawings more fully illustrate this invention."

FIG. 1 is a longitudinal view partly in section of a telescoped caselessround employing a projectile having a rotating band and illustrating thepropellant charge of this invention.

FIG. 2 is a longitudinal view partly in section of a telescoped caselessround having a guilding metal jacket and illustrating the propellantcharge of this invention.

FIG. 3 is a longitudinal view partly in section illustrating theprojectile of the telescoped round of FIG. 2 making contact with therifling in the barrel of a gun.

In FIG. 1 a telescoped round of caseless ammunition comprisingpropellant charge, projectile and primer is shown. The projectile 10 isshown fully contained within the axial bore 12 of propellant charge 14.Projectile 10 has a rotating band 16. The forward end 18 of thepropellant charge is defined by the total area of propellant measuredforward of plane 20 passing through the propellant charge and throughthe contacting surface of rotating band 16. The aft-end 22 of thepropellant charge 14 is defined as that part of the charge measured fromplane 20 passing through the forward surface of rotating band 16 to theaft-surface 24 of the propellant surface charge 14. The projectile 10 issecured at the aft-end of propellant charge 14 in axial bore 12 with aprimer plug 26 containing a primer 28 and an auxiliary ignition charge30 prepared from black powder. The projectile 10 is secured in theforward end of axial bore 12 with a consumable disc 32.

In FIG. 2 a telescoped round having a projectile 34 with a guildingmetal jacket is illustrated. The ogive 36 of the projectile 34 is thecurve defining the shape of the pointed projectile. The base 38 of theogive is the contacting surface of the projectile 34. The sides of theprojectile 40 aft of the base of the ogive are parallel. The outsidediameterof the projectile measured at the base 38 of the ogive 36 isequivalent to the maximum diameter of the projectile. An imaginary plane41 passing through the base 38 of the ogive 36 of the projectile 34 andthrough propellant charge 42 defines the forward surface of the aft-end44 of the propellant charge 42 and thereby defines the forward end 46 ofpropellant charge 42. The propellant charge 42 has an aft surface 48.

In FIG. 3 the telescoped round of FIG. 2 is illustrated in a loadedposition in the chamber of a gun 50. Projectile 34 is illustrated bothin its normal position as fully contained within propellant charge 42prior to firing, and as the projectile would appear as it makes contactwith the rifling in the barrel 52 of a gun. The position of thecontacting surface of the pro jectile 34 is illustrated at plane 54.This contacting surface defined by plane 54 is the same surface as thesurface defined by a plane through base 38 of the ogive 36 of projectile34 in F IG. 2.

The following examples more fully illustrate this invention. All partsand percentages are be weight unless otherwise specified.

EXAMPLE l Propellant charges for caseless ammunition are prepared byplacing smokeless powder granules into a mold and adding a solventmixture to said mold for softening the surfaces of the powder granules,said solvent mixture comprising 40 percent acetone and 60 percent ethylalcohol. The ratio of solvent mixture to smokeless powder is aboutl.0/2.5. After about 1 minute of contact time, the granules arecompression molded to a pressure of 2,000 p.s.i. to form propellantcharges in which the individual smokeless powder granules retain theiridentity. The solvent mixture is driven from the mold duringcompression. The resulting propellant charge is dried to remove residualsolvent. After drying, the propellant charges are machined toappropriate dimensions. These propellant charges contain interstitialpassages between the molded propellant granules.

Propellant charges prepared by the method heretofore described arecoated with burning rate deterrent by partially submerging thepropellant charge in burning rate deterrent solution comprising ethylcentralite (diethyldiphenylurea) dissolved in ethyl alcohol. The totalaft-end of the charge as herein defined is submerged. The ethylcentralite solution readily flows through the interstitial passages inthe propellant charge depositing a deterrent coating on the internal andexternal surfaces of the aft-end of the charge. After about l minutecontact with the burning rate deterrent solution, the propellant chargeis removed from the solution and is dried at 130 F. for about 12 hours.

EXAMPLES 2-9 Following the procedure set forth in example 1, fourpropellant charges molded from two lots of smokeless powder granules arecoated with burning rate deterrent over the entire aft-end of thecharge. The coated propellant charges are loaded with 25 mm. projectilesas shown in the drawing (FIG. 1) and fired. Propellant charges preparedfrom the same lots of smokeless powder are loaded as control rounds.These con-' trol rounds (rounds 4, 5, 8 and 9) are not deterrent coated.Rounds 2, 3, 4 and 5 are prepared from one lot of smokeless powder.Rounds 6, 7, 8 and 9 are prepared from a second lot of smokeless powder.Comparison of ballistic results for these rounds is set forth in table 1below.

TABLE I.COMPARISON OF BALLISTICS DETERRENT COATED AND NON-COATED'IELESCOPED CASELESS AMMUNITION Smokeless Deterrent PropellantProjectile Maximum Results of the firing of rounds 2 and 3 with rounds 4and 5 illustrate an average projectile muzzle velocity increase for thedeterrent coated rounds over the noncoated rounds of 734 feet per secondor about 24 percent increase in velocity. Comparison of ballisticresults of rounds 6 and 7 which are deterrent coated rounds of thisinvention with rounds 8 and 9 (control) illustrate an average projectilemuzzle velocity increase of 492 feet per second or about 14.5 percentincrease in projectile muzzle velocity.

There are many well-known burning rate deterrents for use in controllingthe ignition of smokeless powder. Any of these deterrent materials whichare compatible with the propellant charge of the caseless round andwhich will deter the surface rate of burning of the propellant can beemployed.

The burning rate deterrents must be applied to the propellant charge inthe liquid state. Burning rate C.) which are normally solids can beapplied in solution. Solvents employed with the burning rate deterrentspreferably have no appreciable solvent action upon the propellant chargeand are employed as a carrier for the burning rate deterrents so thatthe interior and exterior surfaces of the propellant charges can becontacted with deterrent. Illustrative burning rate deterrents which canbe employed which are liquids at ambient temperature (22 C.) includedibutyl phthalate, dibutyl succinate, dibutyl adipate, triacetin, ethyldiphenyl phosphate, tributyl phosphate, and the like.

Other burning rate deterrents which can be employed are ethyl centralite(diethyldiphenylurea), methyl centralite (dimethyldiphenylurea),dimethyl phthalate, dioctyl sebacate, butyl benzyl phthalate,dinitrotoluene, and the like. These deterrents are solids at roomtemperature and are employed either above their melting points or insolution. It is preferable to employ normally solid burning ratedeterrents in solution.

Other deterrents which can be employed to control ignition of thepropellant charge of this invention are the well-known surface coatingsfor smokeless powder which are resins that have no appreciable solventaction on nitrocellulose. These resins are applied in the form of asolution which will readily flow through the porous propellant charge ofthe caseless round. Illustrative resins which can be employed include:alkyl esters of the fatty acids, as, alkyl esters of ribinoleic acid,alkyl esters of polymerized ricinoleic acid, etc.; rosin esters, suchas, monohydric alcohol esters abietic acid, polyhydric alcohol esters ofabietic acid, monohydric alcohol esters of pimaric acid, polyhydricalcohol esters of pimaric acid, synthetic lacquer resins, such as, themodified or unmodified polyhydric alcohol-polybasic acid resins (Alkyds,Rezyls), phenolformaldehyde-type resins; rosins, such as, wood rosin,gum rosin; hydrogenated rosins, such as, hydrogenated wood rosin,hydrogenated gum rosin, and the like. Thus, we may use butylricinoleate, butyl acetyl ricinoleate, butyl ester of polymerizedricinoleic acid, methyl abietate, ethyl abietate, hydrogenated methylabietate, hydrogenated ethyl abietate, ester gum, hydrogenated estergum, modified or unmodified glycerolphthalate resin, oil-modifiedphenolforrnaldehyde type resins, glycerol sebacate, glycol sebacate,glycerol-glycol sebacate, modified or unmodified ethylene glycolterpinen maleic anhydride resins, modified or unmodified diethyleneglycol terpinene maleic anhydride resins, modified or unmodifiedtriethylene glycol terpinene maleic anhydride resins, modified orunmodified glycerol terpinene maleic anhydride resins, and the like.

Illustrative solvents for burning rate deterrents which have noappreciable solvent action for propellant charges prepared from moldedgranules of smokeless powder are ethyl alcohol, propyl alcohol,isopropyl alcohol, petroleum hydrocarbons such as benzene and petroleumether, ethyl alcohol containing a minor amount of alkyl acetate such asethyl or butyl acetate, and the like.

The amount of burning rate deterrent applied to the aftend of thepropellant charge of this invention will vary, depending on theparticular burning rate deterrent employed. In general, the deterrentweight applied is from about 0.5 to about 5.0 percent by weight, basedon the weight of the propellant charge. The residence time required todeposit the desired amount of deterrent will vary depending on theparticular deterrent and solvent employed and can be easily determinedby one skilled in the art.

Any convenient method of contacting the aft-end of the propellant chargewith the solution of burning rate deterrent can be employed in thisinvention. A particularly suitable method is submerging or dipping theaft-end of the propellant charge in a bath of burning rate deterrent.

What l claim and desire to protect by Letters Patent is:

l. in a telescoped round of caseless ammunition comprising a propellantcharge having an axial cavity, a projectile completely housed within theaxial cavity and a primer, the improvement comprising a propellantcharge having a forward'end and an aft-end and an aft-surface in whichat least [0 percent of the total internal and external surface area ofthe aft-end of the propellant charge measured from the aftsurface of thepropellant charge is coated with a burning rate deterrent, the aft-endof said charge being defined as that part of the propellant chargebounded from the aft-surface of the charge to the surface of the chargedefined by a plane passing through both the charge and the contactingsurface of the projectile housed within the charge, said contactingsurface being the surface of the projectile initially contacting thebarrel of a gun in which the telescoped round of caseless ammunition isfired.

2. The propellant charge of claini 1 wherein the burning rate deterrentis ethyl centralite.

3. The propellant charge of claim 1 wherein the burning rate deterrentis dinitrotoluene.

4. The propellant charge of claim 1 wherein the burning rate deterrentis dibutyl phthalate.

5. The propellant charge of claim 1 wherein all of the internal andexternal surface area of the aft-end of the propellant charge is coatedwith burning rate deterrent.

6. The propellant charge of claim 5 wherein the aft-end of thepropellant charge is coated with from about 0.5 to about 5.0 percent byweight of burning rate deterrent based on the weight of the totalpropellant charge.

7. The propellant charge of claim 6 wherein the burning rate deterrentis ethyl centralite.

8. The propellant charge of claim 6 wherein the burning rate deterrentis dinitrotoluene.

9. The propellant charge of claim 6 wherein the burning rate deterrentis dibutyl phthalate.

10. The propellant charge of claim 6 wherein the projectile has arotating band having a forward surface and the aft-end of the charge isdefined as that part of the propellant charge bounded from theaft-surface of the charge to the surface of the charge defined by aplane passing through the propellant charge and through the forwardsurface of rotating band of the projectile.

l l. The propellant charge of claim 6 wherein the projectile has aguilding metal jacket and the aft-end of the charge is defined as thatpart of the charge bounded from the aft-surface of the charge to thesurface of the charge defined by a plane passing through the propellantcharge and through the base of the ogive of the projectile.

1. In a telescoped round of caseless ammunition comprising a propellantcharge having an axial cavity, a projectile completely housed within theaxial cavity and a primer, the improvement comprising a propellantcharge having a forward-end and an aftend and an aft-surface in which atleast 10 percent of the total internal and external surface area of theaft-end of the propellant charge measured from the aft-surface of thepropellant charge is coated with a burning rate deterrent, the aft-endof said charge being defined as that part of the propellant chargebounded from the aft-surface of the charge to the surface of the chargedefined by a plane passing through both the charge and the contactingsurface of the projectile housed within the charge, said contactingsurface being the surface of the projectile initially contacting thebarrel of a gun in which the telescoped round of caseless ammunition isfired.
 2. The propellant charge of claim 1 wherein the burning ratedeterrent is ethyl centralite.
 3. The propellant charge of claim 1wherein the burning rate deterrent is dinitrotoluene.
 4. The propellantcharge of claim 1 wherein the burning rate deterrent is dibutylphthalate.
 5. The propellant charge of claim 1 wherein all of theinternal and external surface area of the aft-end of the propellantcharge is coated with burning rate deterrent.
 6. The propellant chargeof claim 5 wherein the aft-end of the propellant charge is coated withfrom about 0.5 to about 5.0 percent by weight of burning rate deterrentbased on the weight of the total propellant charge.
 7. The propellantcharge of claim 6 wherein the burning rate deterrent is ethylcentralite.
 8. The propellant charge of claim 6 wherein the burning ratedeterrent is dinitrotoluene.
 9. The propellant charge of claim 6 whereinthe burning rate deterrent is dibutyl phthalate.
 10. The propellantcharge of claim 6 wherein the projectile has a rotating band having aforward surface and the aft-enD of the charge is defined as that part ofthe propellant charge bounded from the aft-surface of the charge to thesurface of the charge defined by a plane passing through the propellantcharge and through the forward surface of rotating band of theprojectile.
 11. The propellant charge of claim 6 wherein the projectilehas a guilding metal jacket and the aft-end of the charge is defined asthat part of the charge bounded from the aft-surface of the charge tothe surface of the charge defined by a plane passing through thepropellant charge and through the base of the ogive of the projectile.